Electrochemical CO2 Capture by a Quinone-based Covalent Organic Framework

Electrochemical CO2 capture is an emerging technology that promises to be more energy efficient than traditional thermal- or pressure-swing processes. Herein the first evidence of electrochemical CO2 capture using a covalent organic framework (COF) is presented. We hypothesized that the assembly of anthraquinone units into a well-defined porous framework electrode would lead to enhanced electrochemical CO2 capture compared to previous approaches that grafted anthraquinones on carbon supports and suffered from low CO2 capacities and stabilities. To test this, an anthraquinone-based COF is employed, and it is found that the quinones are electrochemically accessible for reversible CO2 capture in an ionic liquid electrolyte. The system achieves a high electrochemical CO2 uptake capacity > 2.6 mmol g-1COF, reaching half of the theoretical CO2 capacity of the material, and surpassing the capacities of anthraquinone-functionalized carbons. The stability and CO2 uptake rate issues encountered with ionic liquid system are also addressed by using aqueous electrolytes where we attained stable carbon capture for 500 cycles with 99.6% coulombic efficiency and an electrical energy consumption of 31 kJ per mol of CO2. The use of covalent organic framework electrodes can become a general strategy for understanding and enhancing electrochemical CO2 capture.